1. Field of the Invention
This invention relates generally to vehicle control systems and more particularly to hydraulic actuator controlled systems for larger vehicles and vessels which control components and steering systems within such environments.
2. Description of Related Art
Larger vehicles, vessels, systems and equipment require hydraulic actuators for the control of components and steering systems therewithin. Mechanical and pneumatic systems and those utilizing electric actuators typically lack sufficient power to deliver linear and rotational forces necessary to operate the components of such larger environments. Typical environments referred to herein would include off-road earth moving equipment, steering systems on larger vessels and ships and equipment requiring hydraulic actuators and hydraulic systems for their component control.
In such conventional hydraulically controlled vehicles, however, high pressure hydraulic fluid lines must be routed to the control mechanisms in proximity to an operator who will manipulate these control mechanisms such as steering wheels and levers to regulate hydraulic fluid flow to the hydraulic actuators. Such systems are complex, expensive and prone to leakage and in use damage which may inhibit fluid flow or cause high pressure fluid line rupture.
One system known to applicant which overcomes such limitations is disclosed in U.S. Pat. No. 4,860,844 invented by O'Neil which teaches a power steering system suitable for large off-highway and other similar vehicles. In this system, no mechanical linkages or hydraulic connections enter the driver's cab. Rather, torque demand signals are produced by an electromechanical torque sensor that measures the deflection of a torsion spring caused by movement of a steering wheel. Hydraulic actuators then respond to the signal produced to properly steer the vehicle.
The following additional patents are known to applicant which are generally in the category of “steer by wire” steering systems as follows:    U.S. Pat. No. 6,219,604 to Dilger    U.S. Pat. No. 5,347,458 to Serizawa    U.S. Pat. No. 5,024,417 to Voxbrunner    U.S. Pat. No. 4,595,867 to Cognevich, Sr.    U.S. Pat. No. 5,253,604 to Bohlin
The present invention provides a preferably visual reference control apparatus for controlling the movement of a hydraulic actuator of a hydraulic control system such as that found in off-road vehicles and in hydraulic steering systems for vessels. A steering wheel is provided which is substantially freely rotatable with the input shaft of a geared transmission which produces higher rotational output speed which, in turn, drives a rotatably actuated voltage generator. The voltage generator will then produce a direct current or d.c. voltage, low current output proportional to the speed that the steering wheel is turned and in the appropriate (+/−) voltage polarity, depending upon direction of steering wheel rotation. This output is then converted into a pulse width modulated (PWM) output current control signal typically required to control the movement of a hydraulic actuator.